By TheStreet.com Staff What Is a Bear Market?A bear market is a time of contraction in financial markets. It is typically defined as a period where prices have fallen 20% from a recent peak. Which prices are being measured? Analysts usestock market indexes as a bellwether to paint a picture of broader economic trends. In particular, the S&P 500 contains 500 of the largest companies trading in America, and its performance is often used as a representative benchmark. While bear markets usually describe a period when the S&P 500 falls 20%, the term can also be used when analyzing the performance …